Well I would worry abotu whether the PS3 will outsell the 360 on a WW weekly basis before worrying about when the PS3 will overtake the 360 in total sales.
A couple numbers to think about, the PS3 is 7.1 million units behind the 360 on WW basis. The PS3 has outsold the 360 on a WW Weekly basis 5 times (not including the PAL launch). The PS3's sales were slightly above 2 of those weeks and the other 3 weeks it sold around 40-60k more. That period coincided with the dubious first price cut. Given that outselling the 360 by 60k a week seems to be the limit fo the PS3's abilities it would take almost 2 years and 4 months of such sales for the PS3 to overtake the 360.
I think we all agree the 360 will outsell the PS3 for the rest fo the year, that would put the sales difference between the two at about 8.5 million at the end of the year. Assuming the PS3 outsell the 360 by 60k a week starting then it would be Oct 2010 before the PS3 outsells the 360.
So no outselling the 360 this year isn't possible, outselling the 360 next year is very very unlikley, outselling the 360 in 2009 is very unlikely, and outselling the 360 this generation is at this point unlikely.
EDIT- Whoops, sorry, misread the title somehow :P.







